PCT Patent Publication WO 03/016283 discloses a process of preparing pyrazoles of Formula i
wherein R1 is halogen; R2 is, inter alia, C1-C4 alkyl, C1-C4 haloalkyl, halogen, CN, C1-C4 alkoxy or C1-C4 haloalkoxy; R3 is C1-C4 alkyl; X is N or CR4; R4 is H or R2; and n is 0 to 3, provided when X is CH then n is at least 1 which are useful as intermediates to insecticides. The method involves treatment of the corresponding 2-pyrazoles of Formula ii with an oxidizing agent optionally in the presence of acid.
When X is CR2, the preferred oxidant is hydrogen peroxide; and when X is N, the preferred oxidant is potassium persulfate. However, the need continues for new methods that are less costly, more efficient, more flexible, or more convenient to operate.